Wooden propeller.



P. BORRMANN.

WOODEN PBOPELLBR.

APPLIOATION FILED 11:13.?, 1911 WTA/isms: [NIH/TOR Patented Dec. 19,1911..

PAUL BORRMANN, or EERIJN, GERMANY.

WOODEN :PROPELLER Specification of Letters Patent.

` Patented Dec. 19, 1911.

Application filed February 7, 1911. Serial No. 607,037.

4To all lwhom it may concern:

-Be it known that I, PAUL BORRMANN, a subject of the German Emperor, andresiding at Berlin, Germany, have invented certain new and usefulImprovements in Wooden Propellers, of which the following is aspecification. v My invention relates to wooden propellers for airships,flying-machines and the like.

Wooden propellers for aerial craft are already well-known having bladescomprising narrow boards running in the direction of the blades. Inthese propellers the boards are superposed in the shape of a fan andthen glued together in layers at right angles to the axis of rotation,whereupon they are worked into the required shape of the blade. Thisknown mode of manufacture has various disadvantages Firstly, as iswellknown, in the case of airpropellers it is exceedingly important tomake the section of the blade as thin as possible and,particu larly, tomake the ends as sharp as possible. When the known mode of gluing theboards together was employed, however, after` ob taining the correctspiral shape there remained atthe outer ends of the blades so few gluedjoints that they could not be made as thin as was required. Secondly, itis well-known that it is preferable to make v the two blades of onepropeller at a small definite angle to one another, in order to negativenot only the action of centrifugal force, but also that o1 the thrust ofthe blades. Such a slanting position of the blades could not be obtainedwhen the propellers were made in the manner known heretofore. In thisevent a large portion of the outer ends of the blades would have beenrobbed of'its connection with the hub owing to wedge-shaped pieces beingformed, there being, in addition, no continuous wood fibers running fromthe end of the blade to the hub.

A primary object of my inventiov is to provide a wooden propeller, towhich these defects are not attached.

According to my invention the two opposite blades of apropeller consistof continuous wooden rods which run in the direction of the blades and,in contradistinction to the blades known heretofore, are glued one withanother in layers parallel to the axis of rotation of the propeller. Inthis manner I obviate the above mentioned disadvantages and obtain, inaddition, the advantage that the number of the glued joints isconsiderably increased just at the places subjected to the greatestbreaking strain. In this manner greater strength and security fromwarping is obtained particularly owing to its being possible to connecttogether a large number of pieces of wood having the grain in variousdirections.

One illustrative embodiment of my invention is represented in theaccompanying drawing, wherein z- Figure l is a plan of a completepropeller,

comprising two blades, Fig. 2 is a section,

enlarged, on the line AA in Fig. 1 and Fig. 3 is a plan, enlarged,showing the outer end of a blade, parts of the veneers being brokenaway.

Referring to the drawings, my propeller comprises a plurality of fiatwooden rods or bars a which run in a direction longitudinally of theblades proper ofthe propeller and are disposed in layers, said layersbeing extended in a direction parallel to the axis of rotation of thepropeller. These wooden rods are made according to a templet having theform of the blade and are firmly glued together. In order to give theblades greaterstrength and stiffness, I glue on both sides of leachblade transverse veneer ZJ and over the layers, said layers beingextended in a direction parallel to the axis of rotation of `thepropeller, a transverse veneer arranged at right angles to the rods andglued on both sides of the blades, and a longitudinal veneer arranged atright angles to said transverse veneer glued on the latter,substantially as shown.

3. A Wooden propeller of the character In testimony whereof, l aiiix mysignadescribed consisting of flat Woolden1 bari ture in the presence oftwo Witnesses. which run in a direction longituL ina ly o the bladesproper of the propeller, and are BORRMANN glued one with another inlayers, said layers Witnesses: being extended in a direction parallelVto HENRY HASPER, the axis of rotation of the propellers. WOLDEMARHAUPT.

Copies of this patent may be obtained for ve cents each, by addressingthe Commissioner of Patents, Washington, D. C.

